Igniting composition containing a pyrogenic oxide



IGNITING coMPosrrroN coN'rAmrNG A PYROGENIC oxma Charles A. Stokes, Wellesley Hills, Mass., assignor to Godfrey L. Cabot, Inc, Boston, Mass, a corporation of Massachusetts No Drawing. Application March 24, 1955 Serial No. 496,620

7 Claims. (Cl. 44-7) This invention relates to combustible pastes and more particularly to substantially odorless but readily inflammable thickened. liquids having particular utility as igniters for diflicultly ignitable combustible solid fuels such as lumps of coal, wood, charcoal, etc.

There has long been a need for a safe, convenient lighting material to use in starting charcoal fires, coal and wood fires in fireplaces and furnaces and for miscellaneous cases in which burnable but not easily ignitable materials are to be set afire. Such an igniter should be in the physical form of greatest convenience for use and for packaging in a safe, cheap, convenient package. These requirements rule out a combustible liquid as neither safe nor convenient because of the likelihood of breakage and spillage and because regardless of how applied, liquids spread out uncontrollably and rapidly evolve vapors in sufiicient amounts to form explosive mixtures with air. A solid igniter can not be spread around to a suitable degree and will not adhere to the material to be ignited so that solids are not convenient to use. Furthermore, it is hard to find a solid material that will burn quickly and intensely at atmospheric pressure.

I have discovered a safe but readily ignitable paste which has just the right balance of properties for an ideal all-purpose igniter. It has a desirable thixotropic plasticity which enables it to be extruded easily from a tube and/or to be brushed or spread upon the surface to be ignited. This past clings to the fuel to which it is applied and will not drop off even when it becomes heated as it necessarily does during the process of burning. It is odorless, nonstaining, nontoxic, easily applied and adherent, yet form-retaining after application even to undersides or vertical surfaces. The ideal igniting compound should be readily ignitable by a match and should burn with a hot flame for a sufiicient length of time to ignite the solid fuel to which it is applied.- Yet it should have a relatively low and controlled volatility so that it can be readily and safely handled, stored and transported. All of these qualities are found in the novel composition of my invention.

It is the principal object of this invention to provide a substantially ordorless fuel for igniting any combustible material.

It is another object of this invention to provide a combustible paste which will adhere to any surface on which used and which will efliciently ignite any combustible material.

It is a further object of this invention to provide an igniting compound which can be conveniently and safely packaged and yet which is readily available for use when needed.

I have discovered that the above objects are realized in the igniting compound of this invention which is made by dispersing in a liquid fuel base of required character as specified hereinafter certain proportions of finelydivided pyrogenic oxides of metals or metalloids selected- 2,902,351" Patented Sept. 1, 1959 ICC 2 from the group consisting of aluminum, titanium, zirconium, and silicon. By finely-divided pyrogenic oxides is meant nonhydrated and substantially anhydrous (i.e., not over about 5% volatile matter) oxides having an' average discrete particle size of not over millimicrons, preferably less than 50 millimicrons, and produced by vapor phase hydrolysis or oxidation of compounds of the corresponding metals and/or metalloids.

Such vapor phase reactions are generally carried out at temperatures of about 1000 F. or higher. For example, halides or other vaporizable compounds of one or more of the stated elements (Al, Zr, Ti and Si) may be mixed with high temperature steam or carried into a combustion zone in which excess oxygen is present or in which high temperature Water vapor is being produced by combustion of a hydrogen-containing fuel. The resultant reaction produces a fine aerosol of solid oxides or mixed oxides in gaseous by-products from which the oxides may be recovered in aerogel form made up of very small discrete particles. Since the gaseous by-products are separated from the solid oxide at temperatures above that at which any of said by-product condenses, the resultant oxides are not hydrated and, instead, are very pure and substantially anhydrous. For example, silica produced in this way is about 99% pure, while alumina of this type usually contains about 5% or less volatile matter.

The liquid fuel base into which the said finely-divided pyrogenic oxides are incorporated according to this invention is composed predominantly of nonaromatic hydrocarbons having the following specifications:

Distillation range:

I.B.P. 300-500 F. E.P. 600 F. maximum. Flash point 100 F. (closed cup), minimum, to

260 F. (open cup) max. Saybolt +15 minimum. Specific gravity 0.76 to 0.85 (55 to 35 A.P.I.) Sulfur 0.05% maximum. Smoke point 25 mm., minimum. Aniline point F., minimum.

There appears to be some relation between the flash point and the initial boiling point which can be given approximately by the following expression (in degrees Fahrenheit):

Flash point =0.79 (I.B.P.)--l36 F Therefore, it is generally not necessary to measure flash points in order to determine the suitability of a given liquid fuel for use in this invention provided the initial boiling point is known.

Similarly, it is not necessary to measure aniline point if the essentially nonaromatic character required of the liquid fuel base for use in the present invention can be ascertained in other ways. For example, in place of a minimum aniline point value of about 155 F., there can be specified a maximum kauri butanol value of about 31, or a minimum content of acyclic compounds of about 70% coupled with a maximum content of aromatic compounds of about 3%.

Combustible nonhydrocarbon liquids which are sub stantially free of elements other than C, H and O can be included in minor proportions in the composition of this invention. When so used they should not constitute more than about 5% by Weight of the hydrocarbon constituent for ethanol and compounds of like volatility nor more than about 20% by weight for butanols and similar or higher molecular weight alcohols, ketones, etc. However, the preferred liquid fuel is composed almost entirely of hydrocarbons.

Although the full range of useful hydrocarbon types is set by the properties listed in the table above, I have found that hydrocarbons having properties in the following range are preferred in the practice of this invention.

Distillation range:

I.B.P. 325-400 F. E.P. 500 F. maximum. Flash point 120 F. (closed cup), minimum, to

180 F. (open cup), maximum. Aniline point 170 F. minimum.

A minimum aniline point of about 170 F. corresponds approximately to a maximum kauri-butanol value of about 28. A liquid hydrocarbon fuel base meeting these values will contain, in general, less than 1% aromatics by weight and at least 75% by weight acyclics. In other words, parafiin type naphthas and other paraffin hydrocarbons are especially useful in the present invention and those containing over 90% acyclics are ideal. A completely odorless fuel base is preferred and one of the best types is made by alkylating a basically suitable (i.e. paraffinic) but odorous petroleum fraction by means of reaction with olefins.

The proportions in which the finely-divided pyrogenic oxides are incorporated in the above liquid fuel bases in order to make the paste-form igniting compounds of this invention varies between about 5 and 20%, and preferably between about 6 and 15% by weight of the total composition. The exact amount used in any given case depends on the nature of both the liquid fuel base and the particular oxide. Thus, the smaller the average particle size of the pyrogenic oxide and/or the larger the amount of nonhydrocarbon liquid in the fuel base the smaller the proportion of the solid oxide generally required to achieve a given amount of thickening. Moreover, pyrogenic silica is much more effective in its thickening action than the other oxides so that the larger the concentration of silica in the pyrogenic oxide used, the smaller the amount of oxide required. For example, using straight silica as the pyrogenic oxide, the proportions are about 5 to 12% and preferably 6 to by weight of the total composition.

Igniting pastes made with pyrogenic silica as the sole pyrogenic oxide or with mixed pyrogenic oxides in which silica is the predominating ingredient (i.e. amounts to over 50% by weight of the mixed oxide) are decidedly superior and are greatly preferred embodiments of this invention. Not only are such pastes made of proper consistency with less total concentration of the solid oxide ingredient but they are also more stable and resistant to bleeding or changes in consistency with time, temperature changes or other variables. Mixed oxides may be either mechanical mixtures of two separate pyrogenic oxides or a single uniform product containing two oxides coformed in a single pyrogenic process.

Specific examples of preparations within the scope of this invention are described below. It should be understood that these examples are given for illustrative purposes and are not to be construed as limitations on the scope of the present invention.

Example 1 To 920 grams of odorless mineral spirits having a specific gravity of 0.76, a flash point (closed cup) of 125 F., and an aniline point of 186 F. is added gradually with stirring 80 grams of fluffy pyrogenic silica having a purity of about 99.5% SiO by weight and an average particle size of about 20 millimicrons. The resultant mixture is a nearly colorless iridescent adherent paste which is form-retaining and yet has a highly thixotropic plasticity which permits it to be easily spread or extruded. It is readily filled into collapsible tubes from which it can be squeezed onto the exact point of application desired, at which point it will remain unless disturbed by external mechanical force. It can then be ignited by a match and will burn intensely at the said localized spot without melting or spreading under the influence of heat or gravity. Jellied fuels made with soaps as thickening agents do not exhibit this superior form retention of the igniting pastes of this invention. Instead such soap-thickened fuels, e.g., napalm, liquify or melt and drip or spread away soon after being ignited. Apparently the soap-fuel gel structure breaks down at about 250 F.

One accurately measured level teaspoon of the above compound was placed in a single mass on a perforated metal plate beneath a mound of hardwood charcoal lumps (about 1 to 1 /2 lbs.). This small body of paste burned without change of shape with an intense flame for almost 4 minutes and the residue continued to glow bright red after that. After about 10 minutes the entire lower part of the mound of charcoal was glowing brightly. Even quicker ignition of a charcoal bed is obtained by using somewhat more paste and smearing it directly on the surfaces of several lumps of charcoal scattered throughout the bed.

The same experiment was tried using unthickened odorless mineral spirits poured directly on the charcoal and ignited. The flames lasted only about two minutes and after three minutes the entire bed was black with no trace of burning.

In place of the straight mineral spirits, there can be used as the fuel base in the above example mixtures of said mineral spirits with nonhydrocarbon aliphatic organic compounds with about the same results. For example, such mixture could contain about 5% by weight isopropanol or about 10% by weight glycol ethyl ether or about 15% by weight methyl isobutyl ketone, etc.

Example 2 To 450 grams of odorless heavy mineral spirits having a specific gravity of 0.77, a flash point (closed cup) of 135 F. and an aniline point of 184 F. is added gradually with stirring 50 grams of fluffy mixed pyrogenic oxides containing about 2% volatile matter by weight (1000 F.) and analyzing about 50% by weight SiO and 47% by weight A1 0 said fluffy oxides having an average particle size of about 40 millimicrons. The resultant product is a white plastic paste which is adherent and form-retaining when left undisturbed and yet is easily handled, spread and/ or extruded under pressure.

Mixed oxides containing TiO or Zr0 can be substituted for the mixed oxide in the above example provided SiO also constitutes about 50% or more of such mixed oxides. However, if mixed oxides containing considerably less than 50% SiO or mixed or straight oxides substantially free of SiO are used, then 60 to 100 grams of such oxides should be substituted for the 50 grams of the oxide used in the above example. The active pyrogenie oxides of the type specified for use in this invention may also be extended with a minor proportion of coarse inactive solid fillers having only an absorbent or drying action instead of real thickening action. Such fillers may, for example be diatomaceous earth, talc, clay, etc. Their usage will permit some reduction in the amount of pyrogenie oxide employed without significant loss in valuable thixotropic plasticity of the igniting paste.

The odorless mineral spirits described in the above examples are most commonly obtained by alkylation, a process by which a pure, synthetic iso-paraffin is made by combining an olefin and a paraffin, or by further refining of normal kerosene fractions, e.g., by steam or fraction distillation. However, certain heavier cuts of normal kerosene fractions from highly parafiinic crudes may meet ignited with a match and burns with a hot but low steady flame. No odor is detected. The selected briquets will be completely ignited within about five minutes and, depending upon how much paste is used, the whole charcoal bed can be completely ignited within about 5 to 20 minutes.

It will be obvious that the novel compound of my invention is of very considerable utility. Heretofore, it has been necessary to light such charcoal fires by means of kindling wood which is very messy and inconvenient to store and handle, or by liquid fuels such as kerosene, alcohol and the like which are dangerous both to use and store. On the other hand, the paste of my invention can conveniently by packaged in tubes such as those used for packaging toothpaste and can be extruded from the tube by simply pressing the opposite end to deliver any desired quantity of paste. Furthermore, the storage of this material is completely safe.

Another advantage of this material is that it will adhere to any surface, hence will be confined to the area of use and will not spread dangerously as will fluid igniters.

It may be noted also that the metal oxides constituting one element of the compound have an additional function which increases the efliciency of my novel material. From observed effects it appears that such oxides catalyze combustion to provide a hotter flame and more efiicient combustion, all of which not only insures fast ignition and complete combustion of the main fuel but also tends to prevent smoke and odors which are ordinarily attendant upon the burning of combustible materials.

Finally, it is apparent that the range of hydrocarbons defined above is critical in providing the odorless characteristic of the material.

The novel paste of my invention has many other uses than the ignition of charcoal fires. It can, for example, be used to ignite coal in coal burning furnaces, stoves and fireplaces; it will also ignite the heaviest logs in fireplaces without the use of kindling. It is particularly valuable as an igniter for materials which are very diflicult to ignite, such as green wood, wet charcoal and other fire resistant materials.

Having thus described my invention, I claim:

1. A stable combustible paste which is not deformed by heat or the ordinary forces of gravity but which has a soft plastic consistency enabling it to be easily spread under the influence of slight pressure or mechanical force, comprising an essentially odorless and nonaromatic paraflin-type naphtha, said naphtha being composed predominantly of nonaromatic organic compounds containing no elements other than C, H and O, at least 80% by weight of said naphtha being made up of hydrocarbons, said naphtha meeting the following specifications: flash point between100-260 R; specific gravity between 0.76-0.85, and aniline point of at least 155 F.; and in amounts from about 5 to about 20% by weight of the total composition substantially anhydrous finely-divided pyrogenic oxides of elements within the group consisting of Al, Zr, Ti and Si.

2. A stable combustible paste as in claim 1 in which the paraflin-type naphtha is composed substantially entirely of hydrocarbon compounds and meets the following specifications: flash point between 120 to 180 F.; specific ggagzit between 0.76 to 0.85, and aniline point of at least 3. A stable combustible paste as in claim 1 in which the finely-divided pyrogenic oxide is predominantly composed of Si0 and the concentration of said oxide in the total composition is between about 6 and 12% by weight.

4. A stable igniting paste having a desirable thixotropic plastic consistency and suitable for use in initiating combustion of solid fuels comprising as to by weight of the total composition a paraflin-type naphtha containing at least 75% by weight of said naphtha of acyclic compounds and not over 1% by weight of said naphtha of aromatic compounds, said naphtha having a flash point of at least F., and, as 5 to 12% by weight of the total composition, substantially anhydrous pyrogenic silica having an average particle size of less than about 100 millimicrons.

5. A stable igniting paste containing 90 to 94% by weight hydrocarbon having a flash point of at least F. and an aniline point of at least F. and 6 to 10% by weight of substantially anhydrous pyrogenic silica having an average particle size of less than about 50 millimicrons.

6. A stable igniting paste as in claim 5 in which the hydrocarbon fraction contains at least 90% acyclic compounds and not over 1% aromatic compounds.

7. A stable igniting paste as in claim 5 in which the hydrocarbon fraction is composed substantially entirely of pure synthetic iso'paratfin type compounds.

References Cited in the file of this patent UNITED STATES PATENTS 1,523,580 Calvert Jan. 20, 1925 2,093,454 Kistler Sept. 21, 1937 2,399,687 McNabb May 7, 1946 2,530,493 Van Loenen Nov. 21, 1950 2,655,476 Hughes et a1. Oct. 13, 1953 OTHER REFERENCES K-3 Silicon Dioxide for Rubber Filler, Field Information Agency Technical (Final Report 743), Oflice of Military Government for Germany (U.S.), April 24, 1946. (Obtainable from Documents Distribution Center, U.S. Department of Commerce, Washington, DC.)

Industrial Solvents, Mellan, Reinhold Pub. Corp., N.Y., 2nd ed. (1950) page 247. 

1. A STABLE COMBUSTIBLE PASTE WHICH IS NOT DEFORMED BY HEAT OR THE ORDINARY FORCES OF GRAVITY BUT WHICH HAS A SOFT PLASTIC CONSISTENCY ENABLE IT TO BE EASILY SPREAD UNDER THE INFLUENCE OF SLIGHT PRESSURE OR MECHANICAL FORCE, COMPRISING AN ESSENTIALLY ODORLESS AND NONAROMATIC PARAFFIN-TYPE NAPHTHA, SAID NAPHTHA BEING COMPOSED PREDOMINANTLY OF NONAROMATIC ORGANIC COMPOUNDS CONTAINING NO ELEMENTS OTHER THAN C, H AND O, AT LEAST 80% BY WEIGHT OF SIAD NAPHTHA BEING MADE UP OF HYDROCARBONS, SAID NAPHTHA MEETING THE FOLLOWING SPECIFICATIONS: FLASH POINT BETWEEN 100-260* F., SPECIFIC GRAVITY BETWEEN 0.76-0.85, AND ANILINE POINT OF AT LEAST 155* F., AND IN AMOUNTS FROM ABOUT 5 TO ABOUT 20% BY WEIGHT OF THE TOTAL COMPOSITION SUBSTANTIALLY ANHYDROUS FINELY-DIVIDED PYROGENIC OXIDES OF ELEMENTS WITHIN THE GROUP CONSISTING OF AL, ZR, TI AND SI. 